Discussion
Formaldehyde emission from a board falls with a half-life of 2 years. After 6 years the emission rate is
Answer: B
Correct answer: One eighth of the original
Six years is three half-lives:
\[ \frac{6}{2} = 3 \qquad \left(\frac{1}{2}\right)^{3} = \frac{1}{8} \]
The distractor "one third" divides the years by the half-life and inverts, treating the decay as linear. The exponential decline is why formaldehyde from new pressed wood is worst when the material is new, and why the problem diminishes over years without any intervention - though warmth and humidity both accelerate the release.
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